The accused man, Jay Michaud, was arrested in 2015 suspected of visiting the child pornography website Playpen via the Tor browser. Despite the alleged anonymity of Tor, Michaud was identified after the FBI took control of Playpen for nearly two weeks.

The FBI used a form of malware known as a ‘network investigative technique’ (NIT) to track Michaud and 135 other suspects who are also facing prosecution, reported the IBT Times.

When users logged into the Playpen website a NIT program would send communications to their computer which would trigger identifying data being relayed back to the FBI.

How NIT’s operate was not fully disclosed, prompting Michaud’s defence attorney to request access to their source code.